Data Representation

Question 1

What is meant by a charecter set?

Answer 1

A group of charecters which can be represented or coded

Question 2

How many charecters can be represented with the 7-bit ASCII

Answer 2

128 charecters.

Question 3

What is meant by a bit?

Answer 3

The smallest unit of data a computer can use.

Question 4

What is the highest value that can be represented by a nibble?

Answer 4

1111

Question 5

How many bits are there in a byte?

Answer 5

8 bits

Question 6

How many bytes does 12 bits make?

Answer 6

1.5 bytes

Question 7

How many megabytes are there in 3 gigabytes?

Answer 7

3000

Question 8

An overflow error can occur when adding two 8-bit binary values. What is meant by an overflow error?

Answer 8

When the total from adding numbers cannot be stored into the CPU.

Question 9

Why do people use hexadecimal values to represent numbers stored in computers?

Answer 9

Hexadecimal numbers use less memory so more can be stored.

Question 10

Why is a check digit used?

Answer 10

To check for errors.

Question 11

What does ASCII stand for?

Answer 11

American Standard Code for Information Interchange.

Question 12

Why would Extended ASCII be used?

Answer 12

Extended ASCII would be used for special charecters and has more charecters than ASCII.

Question 13

What is meant by Unicode?

Answer 13

Unicode is large set of charecters which is used widely because it supports different languages.

Question 14

What is meant by a Pixel?

Answer 14

The smallest identifiable area of an image.

Question 15

How many colours can be represented in an image with 8 bits?

Answer 15

256 colours.

Question 16

Why is metadata included in a file?

Answer 16

The reason why metadata is included in a file is to show information about a picture.

Question 17

How does the resolution of an image affect the size of the file?

Answer 17

The higher the resolution, the larger the file size will be.

Question 18

Sampling intervals and other factors affect the size of a sound file and the quality of its playback. What is meant by a bit rate?

Answer 18

The number of bits which determines the range of colours.

Question 19

How can sound be sampled and stored in digital form?

Answer 19

An analogue converter will capture a sound wave at regular time intervals.

Question 20

Compression is often used to reduce the size of files before sending them electronically. What is one advantage for compressing files in this way?

Answer 20

To save storage space on media.

Question 21

What is meant by lossy compression?

Answer 21

Lossy compressions permanently removes some data or uncompressed data is not the same as the original.

Question 22

What is meant by loseless compression?

Answer 22

Lossless compression does not store repeated data and removes it, allows the original file to be reconstructed the same and has a larger file than lossy compression.

Question 23

What’s one file standard?

Answer 23

PDF, JPG, GIF, PNG, MP3

Question 24

How to calculate a file size of a text file

Answer 24

Bits per character X number of characters

Question 25

How to calculate the file size of a sound file

Answer 25

Sample rate x Duration (s) x bit depth

Question 26

What is meant by the resolution of an image?

Answer 26

Resolution is the concentration of pixels within a specific area.

Question 27

Describe what’s meant by colour depth

Answer 27

It determines how many colours can represented in an image.

Question 28

Give two examples of metadata

Answer 28

Date and time (location can be allowed)

Question 29

State 2 factors that can affect the file size of a bitmap image

Answer 29

The amount of pixels and colour depth.

Question 30

Explain the relationship between the image quality and file size.

Answer 30

The higher the image quality, the bigger the file size because better quality , resolution and colour depth increase the size

Question 31

Describe what’s meant by sound sampling

Answer 31

Taking measurements of amplitude of the wave at regular intervals. These are stored in binary.

Question 32

The length of a recording will heavily influenxe the size if the sound file. State two factors other than recording length that determine the file seize of a recording

Answer 32

The frequency per second affects the level of detail in digital representation. The greater the frequency, the greater accuracy.

Question 33

The sampling frequency is the frequency with which measurements are taken more often within the same period of time. How would this affect the quality of the recording?

Answer 33

The more frequently we sample the sound and the more accurately we record the sound wave.

Question 34

Explain the relationship between the quality of the playback and the file size

Answer 34

As the quality increases, owing to a greater number of samples or a greater sampling accuracy, the more data generated, an therefore the larger the file size

Question 35

Give two reasons why you might compress photographs files before emailing them to a friend.

Answer 35

To save storage space and to reduce transmission times when sending on a network such as the internet.

Question 36

Describe 2 benefits of lossy and lossless compression.

Answer 36

Lossy - Allows data to be transmitted faster over a network and suitable for images/video/sound.

Lossless - Removes repeated data and suitable for text/ code files.